Well, the error says that your query is wrong, so that's a good place to start. ;) My guess would be because Access is having trouble parsing "Tel number", and surrounding it with brackets would fix the problem:

This is assuming "Tel number" actually has embedded whitespace in the database schema. Otherwise it's a typo and you need to remove that space. I mention this as an alternative because UserName doesn't have a space, which suggests either an inconsistent schema definition or a typo in the C# code.

But typically when getting errors like this I'll trace the query or print out the end result that gets run, then copy/paste and run it directly from the database. Often it's easier to debug from there than simply going by the stack trace in C#.